The present invention relates to a control circuit which can raise the frequency of the reference clock signal of a stepping motor to obtain a higher speed of operation for the motor.
A stepping motor which receives a reference clock signal has been often employed in the driving portion of equipment such as X-Y plotters and printers in which a movable object needs to be precisely located in a predetermined place in response to an input signal.
Accordingly, in order to raise the moving speed of the movable object without degrading the resolution (the amount of movement per pulse of the input reference clock signal) in such equipment, the frequency of the reference clock signal must be raised. In order to increase the speed of the movable object by raising the frequency of the reference clock signal, however, a stepping motor of excellent high-speed response characteristics must be used. This has led to the disadvantage that a sharp increase in cost is involved.
Even in the case where a stepping motor of good high-speed response characteristics is employed by allowing for the increase in cost, the frequency of the reference clock signal needs to be raised from a low magnitude to a high magnitude during the starting operation when the frequency of the reference clock signal is made high. This has led to the disadvantage that the control circuit becomes complicated to further increase the cost.